1. Field of the Invention
This invention relates to the field of telecommunications, and in particular to antenna systems and operational methods.
2. Description of the Prior Art
Antennas are used to receive and transmit signals that comprise electromagnetic waveforms. Electromagnetic waveforms have two distinct fields, an electric field and a magnetic field. The electric field and the magnetic field are orthogonal to one another and determine a polarization of a signal. An example of a polarization of a signal is horizontal polarization. Horizontal polarization includes an electric field that is horizontal to a receiver as the signal is being received. Antennas are configured to either receive or transmit a signal based on the polarization of the signal. In many instances, a single antenna is used to either receive or transmit an individual signal of a particular polarization.
Many signals are used in communication systems. The sheer number of signals necessitates diversity among the signals. One form of diversity includes spatial diversity. Spatial diversity includes separating antennas by some predetermined distance to assist in preventing interference from other signals. Interference can occur when a signal intended for one antenna on a platform is received by another antenna on the same platform. An example of spatial diversity includes configuring an antenna platform to have multiple antennas spaced apart from one another for receiving and/or transmitting individual signals of a single polarization. Unfortunately, providing multiple antennas is costly and increases a physical load placed on the platform. Furthermore, antenna platform space is typically limited and spatial diversity increases platform size.
The invention helps solve the above problem and others by providing an antenna system for use in a communication system. The antenna system includes a first antenna and a second antenna The first antenna receives a signal having a first polarization. The second antenna receives a signal having a second polarization and a signal having a third polarization. The second polarization is rotated from the first polarization and the third polarization is rotated from the second polarization.
In an embodiment, the second polarization is rotated substantially forty-five degrees from the first polarization. In other embodiments, the third polarization is substantially orthogonal to the second polarization. In another embodiment, the first antenna is configured to receive a signal having a polarization that is substantially orthogonal to the first polarization. In one embodiment, the first antenna is configured to transmit a signal having the first polarization. In other embodiments, the first antenna is configured to transmit a signal having a polarization that is substantially orthogonal to the first polarization. In other embodiments, the second antenna is configured to transmit a signal having the second polarization. In another embodiment, the second antenna is configured to transmit a signal having the third polarization. In one embodiment, the antenna system includes a third antenna configured to receive a signal having the first polarization. In another embodiment, the third antenna is configured to transmit a signal having the first polarization. In other embodiments, the third antenna is configured to receive a signal having a polarization that is substantially orthogonal to the first polarization. In one embodiment, the third antenna is configured to transmit a signal having a polarization that is substantially orthogonal to the first polarization. In another embodiment, the communication system comprises a wireless broadband communication system. In one embodiment, the wireless broadband communication system comprises a Multichannel Multipoint Distribution System (MMDS). In other embodiments, the antenna system includes a platform for supporting antennas.
Advantages of the following embodiments include reducing a number of antennas for transmitting and/or receiving while preserving antenna diversity. Other advantages include decreasing a physical load placed on an antenna platform.